The layer of air above the Earth is called the atmosphere. It is made of many gases, including oxygen and nitrogen. The atmosphere is made of several layers.
The first layer of the atmosphere is called the troposphere. This is the layer closest to the ground where we live. Most of the water vapor in the air is in this layer. This is where our weather takes place. As you go higher, the temperature of the troposphere decreases.
The next layer is called the stratosphere. This layer contains ozone, which is a special layer of oxygen molecules. They absorb harmful rays of the sun. Sitting on top of the stratosphere is the mesosphere. There is no ozone in this layer. It is very cold here. Temperatures can fall to more than -100 degrees Celsius.